Chlorotrimethylsilane → (E)-3-cyclohexyl-2-(4-methanesulfonyl-3-trifluoromethyl-phenyl)-acrylic acid methyl ester

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

A mixture of zinc dust (1.3 g, 20 mmol, Aldrich, −325 mesh) and dry tetrahydrofuran (2 mL) under argon was treated with 1,2-dibromoethane (187 mg, 1 mmol). Thc zinc suspension was then heated with a heat gun to ebullition, allowed to cool, and heated again. This process was repeated three times to make sure the zinc dust was activated. The activated zinc dust suspension was then treated with trimethylsilyl chloride (110 mg 1 mmol), and the suspension was stirred for 15 min at 25° C. The reaction mixture was then treated dropwise with a solution of (E)-3-cyclohexyl-2-iodo-acrylic acid methyl ester (prepared in Example 4, 2.5 g, 8.5 mmol) in dry tetrahydrofuran (3 mL) over 5 min. After the addition, the reaction mixture was stirred for 1 h at 40-45° C. and then stirred overnight at 25° C. The reaction mixture was then diluted with dry tetrahydrofuran (4 mL), and the stirring was stopped to allow the excess zinc dust to settle down (˜2 h). In a separate reaction flask, bis(dibenzylideneacetone)palladium(0) (108 mg, 0.2 mmol) and triphenylphosphine (209 mg, 0.8 mmol) in dry tetrahydrofuran (10 mL) was stirred at 25° C. under argon for 10 min and then treated with 4-bromo-1-methanesulfonyl-2-trifluoromethyl-benzene (2.12 g, 7 mmol) and the freshly prepared zinc compound in tetrahydrofuran. The resulting brick red solution was heated at 40-45° C. For 2 d. The reaction mixture was cooled to 25° C. and then poured into a saturated aqueous ammonium chloride solution (100 mL), and the organic compound was extracted into ethyl acetate (3×75 mL). The combined organic extracts were washed with a saturated aqueous sodium chloride solution (1×100 mL), dried over anhydrous magnesium sulfate, filtered, and concentrated in vacuo. Biotage chromatography (FLASH 40M, Silica, 9/1 to 3/1 hexanes/ethyl acetate) afforded (E)-3-cyclohexyl-2-(4-methanesulfonyl-3-trifluoromethyl-phenyl)-acrylic acid methyl ester (2.7 g, 99%) as a viscous oil: EI-HRMS m/e calcd for C18H21F3O4S (M+) 391.1191, found 391.1200.

Herkunft & Nachweise